1. Field of the Invention
The present invention relates to a bat for an upright piano, which is supported by a center pin disposed on a bat flange, and strikes a string by swinging a hammer in response to a key touch.
2. Description of the Prior Art
A conventional bat for an upright piano is disclosed, for example, in Laid-open Japanese Patent Application No. 6-27934. This bat, which has a general structure, is provided on a key-by-key basis, in association with a hammer having a hammer head at an upper end thereof, a catcher and the like (hereinafter, the bat, hammer, and catcher are collectively called the “hammer assembly”). The bat has its lower end pivotally supported by a center pin of a bat flange.
The bat flange has bat supports which protrude upward from a left and a right end, respectively, and a center pins extend horizontally between the left and right bat supports. One known bat has a bat body to which a bat plate is attached. In such a bat, the bat body is made, for example, of an ABS resin, and has a lower end which has a width smaller than the remaining part. A groove having a V-shaped cross section is formed in the back surface of the lower end, and laterally extends. The bat plate is attached with the groove in engagement with the center pin which is sandwiched between the bat plate and bat body. In this state, the bat is in engagement with the center pin at a total of three points, i.e., two points on a wall surface above and below the groove of the bat body, and one point on the front surface of the bat plate. In this way, the hammer assembly including the bat is pivotally supported by the center pin, and pivotally moves about the center pin in response to a key touch which causes the jack of an action to push up the lower surface of the bat body. Then, the hammer strikes a string at the back thereof, and vibrates the same, thereby generating a piano sound.
However, the conventional bat described above implies the following problems. In an upright piano, due to the structure of the action, frame and the like, the hammer can be mounted on the bat laterally asymmetrically about the fulcrum of pivotal movements of the bat particularly in a bass area. In this arrangement, the hammer assembly is installed with its centroid laterally shifted with respect to the fulcrum. This results in a moment, during a pivotal movement, which causes the hammer to laterally hobble about the vicinity of the center pin, as indicated by an arrow M1 or an arrow M2 in FIG. 1. As such, loads intensively act on the left and right ends of the center pin, respectively, in the opposite directions to each other from both ends of the groove of the bat body. Thus, as indicated by an arrow m1 or an arrow m2 in FIG. 1, excessive loads act on the both ends of the groove as counter-forces from the center pin, so that the center pin relatively moves outward of the groove along the wall surface of the groove. Consequently, the hammer assembly laterally hobbles and therefore cannot swing with stability. Also, such hobbling can result in deformation of the groove, and a gap between the center pin and groove. In this event, the hammer assembly becomes wobbly, possibly resulting in a failure in stable pivotal movements of the hammer assembly, the inability of the hammer head to strike a string at a proper striking position, and a failure in generating a proper piano sound.
Another conventional bat for an upright piano is formed with a groove in its lower end, which has a semi-circular cross section. A center pin, in contact with an entire wall surface of the groove, is sandwiched between a bat plate and a bat body. In this structure, even when a hammer assembly has the centroid which laterally offsets, a counter-force from the center pin can be supported by the entire wall surface of the groove in a well balanced manner, thus making it possible to prevent deformation of the groove.
However, if the center pin varies in diameter, a gap is developed between the groove and center pin when the diameter is smaller, whereas the center pin cannot be brought into engagement with the groove when the diameter is larger. Therefore, even such variations in diameter that can be generally assumed, can cause rather unfavorable situations in view of the stability.